HIGHLY TOXIC COPLANAR PCB126 REDUCES LIVER PEROXISOMAL ENZYME-ACTIVITIES IN RATS

The effect of the highly toxic coplanar PCB congener, 3,4,5,3',4'-pent achlorobiphenyl (PCB126) on hepatic peroxisomes was studied in rats. T he aim of this study was to investigate whether a toxic dose of the di oxin-like coplanar PCB modifies enzyme activities in peroxisomes where plays an important role in lipid metabolism. Treatment with PCB126, a t a single i.p. administration of 25 mg/kg which evokes clear suppress ion of body weight gain, resulted in marked reduction (to about 40-50% ) of catalase activity and peroxisomal fatty acyl-CoA beta-oxidizing s ystem. Immunoblotting showed that expression of catalase was greatly r educed by the treatment in parallel with the activity. Light microscop y revealed a drastic reduction in granules possessing peroxidase activ ity, while electron microscopy demonstrated that no apparent morpholog ical changes had taken place. Thus the reduction in catalase activity caused by PCB126 could be attributable to suppression of protein expre ssion. The marked reduction of these peroxisomal enzyme activities mig ht be related to hyperlipidemia caused by dioxin-related compounds in rats and humans. (C) 1998 Elsevier Science B.V. All rights reserved.